In this Monday, Aug. 19, 2013, file photo, Oscar Pistorius cries as he prays with his sister Aimee, right, and brother Carl in the magistrates court in Pretoria, South Africa. / AP

by Zaheer Cassim, Special for USA TODAY

by Zaheer Cassim, Special for USA TODAY

JOHANNESBURG, South Africa ‚?? A witness at Oscar Pistorius' murder trial testified Monday she heard "bloodcurdling screams" from a woman and then shots, the first testimony in the trial of the Olympic runner.

"I heard her voice during the shots," said neighbor Michele Burger, a University of Pretoria economics professor.

Pistorius, who shot his girlfriend Reeva Steencamp on Valentine's Day 2013, says he thought she was a burglar when he fired at her. If convicted, the venerated athlete and a double amputee, faces life in prison.

Burger told the Pretoria court she was suddenly woken by a women screaming at 3 a.m.

"I was still sitting in the bed and I heard her screams," Burger said. "She screamed for help. Then I also heard a man screaming for help - three times he yelled for help. I heard the screams again (and) it was more intense‚?¶ she was very scared."

"After, I heard four shots. Four gun shots - bang, bang, bang, bang."

Pistorius has pleaded not guilty to all four charges against him: murder, two charges relating to discharge of a firearm in a public place and one charge of illegal possession of ammunition.

South Africans were shocked last year when Pistorius, one of the country's most famous athletes, was charged with shooting his model girlfriend four times through a toilet door with a pistol.

The case has created a sensation here where Pistorius, known as "Blade Runner" for his carbon-fiber prosthetic legs, is among the most famous athletes in the country.

"I don't know whether the judge will find Oscar guilty or not," said said Silindile Nyathikazi, a 26-year-old media relations manager. "I think there are still a lot of unanswered questions with regards to what happened that night."

Pistorius arrived in North Gauteng High Court wearing a dark gray suit and black tie. Before the trial started he walked past the victim's mother who says she came to court so she can "really look him in the eyes."

Defense lawyer Kenny Oldwadge said in his opening statement that the killing was an accident and that there were inconsistencies in the state's case, as well as an attempt to introduce inadmissible character evidence to discredit him.

He said Pistorius brought two fans in from the balcony on the night of the killing, after speaking to his girlfriend who was in bed beside him. He said Steenkamp must have gone into the bathroom while Pistorious was fetching the fans. Pistorius said he did not notice that she had gone and heard the bathroom window open.

"I approached the bathroom, armed with my firearm, so as to defend Reeva and I," Pistorius said in the statement that was read by his lawyer.

He said he then heard a noise in the toilet, and was in a "fearful state" because he was unable to run away or defend himself physically since he was not wearing his prostheses.

However, the prosecution says some people heard arguing before the shots. But Pistorious' lawyer said that claim was an "unsubstantiated" allegation. According to Pistorius' statement, other neighbors living nearby said they had not heard any argument.

The trial has riveted the attention of the country, Until last week, it was not clear if the trial would be broadcast because the judge felt TV cameras would be a "potentially distracting feature" to witnesses and interfere with a right to a fair trial.

But the judge relented and said some of the proceedings will only broadcast and other portions he said would only be made available to the public via audio.

"This is a big mess, it's huge, but I think if he is guilty he must go to jail," said Nthabiseng Mahlangu, 25, an office administrator.

"Some say he is disabled or he was under the influence, but why should he be set free?"

Others believed he was not entirely at fault.

"I feel sorry for the guy maybe he was on drugs or alcohol or something but I feel like he is showing remorse," said Helen Mokgope, a 53-year-old office cleaner.

The trial is expected to last about three weeks. Pistorius remains free on bail.